/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
using System;

namespace org.apache.commons.compress.compressors.bzip2 {
    /**
     * Utility code for the BZip2 compression format.
     * @ThreadSafe
     * @since Commons Compress 1.1
     */
    public abstract class BZip2Utils {

        /**
         * Map from common filename suffixes of bzip2ed files to the corresponding
         * suffixes of uncompressed files. For example: from ".tbz2" to ".tar".
         * <p>
         * This map also contains bzip2-specific suffixes like ".bz2". These
         * suffixes are mapped to the empty string, as they should simply be
         * removed from the filename when the file is uncompressed.
         */
        private static readonly System.Collections.Hashtable uncompressSuffix = new System.Collections.Hashtable();

        private static void addToUncompressSuffix() {
            uncompressSuffix.Add(".tbz2", ".tar");
            uncompressSuffix.Add(".tbz", ".tar");
            uncompressSuffix.Add(".bz2", "");
            uncompressSuffix.Add(".bz", "");
        }
        // N.B. if any shorter or longer keys are added, ensure the for loop limits are changed

        /** Private constructor to prevent instantiation of this utility class. */
        private BZip2Utils() {
        }

        /**
         * Detects common bzip2 suffixes in the given filename.
         *
         * @param filename name of a file
         * @return <code>true</code> if the filename has a common bzip2 suffix,
         *         <code>false</code> otherwise
         */
        public static bool isCompressedFilename(String filename) {
            if (uncompressSuffix.Count == 0) addToUncompressSuffix();
            String lower = filename.ToLower(System.Globalization.CultureInfo.GetCultureInfoByIetfLanguageTag("en"));
            int n = lower.length();
            // Shortest suffix is three letters (.bz), longest is five (.tbz2)
            for (int i = 3; i <= 5 && i < n; i++) {
                if (uncompressSuffix.ContainsKey(lower.Substring(n - i))) {
                    return true;
                }
            }
            return false;
        }

        /**
         * Maps the given name of a bzip2-compressed file to the name that the
         * file should have after uncompression. Commonly used file type specific
         * suffixes like ".tbz" or ".tbz2" are automatically detected and
         * correctly mapped. For example the name "package.tbz2" is mapped to
         * "package.tar". And any filenames with the generic ".bz2" suffix
         * (or any other generic bzip2 suffix) is mapped to a name without that
         * suffix. If no bzip2 suffix is detected, then the filename is returned
         * unmapped.
         *
         * @param filename name of a file
         * @return name of the corresponding uncompressed file
         */
        public static String getUncompressedFilename(String filename) {
            if (uncompressSuffix.Count == 0) addToUncompressSuffix();
            String lower = filename.ToLower(System.Globalization.CultureInfo.GetCultureInfoByIetfLanguageTag("en"));
            int n = lower.length();
            // Shortest suffix is three letters (.bz), longest is five (.tbz2)
            for (int i = 3; i <= 5 && i < n; i++) {
                Object suffix = uncompressSuffix[lower.Substring(n - i)];
                if (suffix != null) {
                    return filename.substring(0, n - i) + suffix;
                }
            }
            return filename;
        }

        /**
         * Maps the given filename to the name that the file should have after
         * compression with bzip2. Currently this method simply appends the suffix
         * ".bz2" to the filename based on the standard behaviour of the "bzip2"
         * program, but a future version may implement a more complex mapping if
         * a new widely used naming pattern emerges.
         *
         * @param filename name of a file
         * @return name of the corresponding compressed file
         */
        public static String getCompressedFilename(String filename) {
            return filename + ".bz2";
        }

    }
}